The statistics watchdog has written to the Government over the “transparency” of its document setting out plans for a full academisation by 2030.

Ed Humpherson, director general for regulation at the Office for Statistics Regulation, wrote to the Department for Education (DfE) on Wednesday to highlight “issues regarding the transparency, quality and replicability of the statistics” presented in the Government document presenting the case for academisation.

In April, Kevin Courtney, joint general secretary of the National Education Union (NEU), told an annual conference in Bournemouth that the Government’s case for academies “deliberately suppresses” information.

He said the Government’s “case for a fully trust-led system” – its document outlining the benefits of academisation – “deliberately suppresses… that the top 10% of MATs that the Government cites are the ones with the lowest number of children on pupil premium and the highest number of children in grammar schools”.

He described the document as “truly a statistics scandal”.

Mr Humpherson said that in the document – The case for a fully trust-led system – which was published alongside the schools White Paper in March, it was not always possible to identify the data that had been used to produce its analysis.

He added that “insufficient information” on the methodologies used to produce the paper’s statistics made it harder for readers to draw “reliable conclusions”.

“The limited transparency around the data sources and methods means that it is difficult for users to replicate the figures presented and to draw their own conclusions,” he said.

“The Department for Education should ensure that sufficient information is included in the document so that users are able to easily replicate the statistics.

After months of preparation the document it came up with was so flawed that the Office for Statistics Regulation have agreed with the NEU’s complaint that the report is misleading

“Given the high-profile nature of the White Paper that this evidence document supports, the Department for Education should ensure that users have access to key information to be able to understand the data and what this means for the conclusions that can be drawn from the data.”

Mr Humpherson added that he understood the DfE was planning to make changes to the evidence document as well as publishing additional information to “help inform the public debate”.

Mary Bousted, joint general secretary of the NEU, said: “The Government claims that its plan to force all schools to join a multi-academy trust is evidence-led.

“However, after months of preparation the document it came up with was so flawed that the Office for Statistics Regulation have agreed with the NEU’s complaint that the report is misleading.

“This shows that there is no evidence that forcing all schools to join a multi-academy trust will improve schools. It is time for Nadhim Zahawi to withdraw his plan, which is now exposed as wholly ideological, and get back to what teachers and parents actually want the Government to focus on. The White Paper as it stands has nothing to say on the most urgent matters facing education.”

The Government has said it wants all schools to be in MATs by 2030. In March, the NEU said the Government had misreported information in the report through use of data from the top 10% of MATs.